Terminology

Weight Class Definitions;

(Clan BattleMechs are in Blue and italiziced)
InnerSphere Names for Clan Mechs are in ( ) with the wieght following the name
MW2: Mercenaries MW3 MW4
Light;(up to 35 Tons) up to 35 Tons
Adder (Puma) 35 FireFly 30
Owens 30
Flea 20
Cougar 35 Osiris 30
Adder (Puma) 35 Raven 35
WolfHound 35
Medium (40 to 55 Tons) 40 to 55 Tons
ShadowCat 45 Strider 40
Nova (BlackHawk) 50 Bushwacker 55
ShadowCat 45 Chimera 40
Hellspawn 45
Uziel 50
BushWacker 55
Heavy (60 to 75 Tons) 60 to 75 Tons
MadDog (Vulture) 60 Champion 60
Summoner (Thor) 70 Avatar 70
TimberWolf (MadCat) 75 Orion 75
MadDog (Vulture) 60 Argus 60
Hellbringer (Loki) 65 Catapult 65
Summonor (Thor) 70 Thanatos 75
NovaCat 70
TimberWolf (MadCat) 75
Assault (80 Tons and above) 80 Tons and above
SuperNova 90 Sunder 80
DireWolf (Diashi) 100 Annihilator 100
MadCat II* 95 Awesome 80
DireWolf (Diashi) 100 Mauler 90
Atlas 100

*this is most certainly an Inner Sphere Designation only

Weapon configuration modification definitions

Table is for quick reference, see Descriptions below for more detail Common / StarLance BattleZone
Stock C0 T1
Energy only C1 T2
Energy and Ballistics only C2 T4
Missiles and Balllistics only C3 T5
Missiles and Energy C4 T3
Ballistics only C5
Full Mods C6 T6
Missiles only C7

C0 -- Stock weapons; The are the configurations that are shipped with the game and that cannot be deleted. There is always one Stock configuration for each chassis. In MechWarrior2: Mercenaries and MechWarrior4 the first BattleMech in a chassis has no designator. If there are more "stock variants" in MW2 they are simply designated as 'A', 'B', and so on.  In MW3, the "first" stock BattleMech is disignated as Prime, with variants as Alternate A, Alternate B, etc.  In MW4, you only get the one stock.

C1 -- Energy Weapons Only;  This refers to Lasers, Pulse Lasers, PPC's, and Flamers.

C2 -- Energy and Projectile only, No missiles; Any combination of Lasers, Pulse Lasers PPC's,Flamers, LBX, AC, Gauss and Machine Guns.

C3 -- Missles and Projectile only, No energy; Any combination of Lrm, Srm, Ssrm, Narc, LBX, AC,Gauss and Machine Guns

C4 -- Missles and Energy only, No projectiles; Any combination of Lrm, Srm, Ssrm, Narc, Lasers,Pulse Lasers, PPC's and Flamers.

C5 -- Ballistic Weapons Only; Here the weapons are restricted the slug throwing weapons. Machine Guns, LBx, AutoCannon, Ultra AutoCannon, and Guass Rifles.

C6 -- Full Modifications; This means any thing you want to put on that BattleMech you can.

C7 -- Missiles only; AMS and Narc can be used in this category also since they are in support of (Narc) or defend against (AMS) missile weapons.